Research Journal of Applied Sciences, Engineering and Technology 3(8): 752-755, 2011
ISSN: 2040-7467
© Maxwell Scientific Organization, 2011
Received: May 21, 2011
Accepted: July 02, 2011
Published: August 30, 2011
Investigation into Trace and Major Elements of “Hyire” (Kaolin) Widely used in
Ghana Using Neutron Activation Analysis
1
R.G. Abrefah, 2L.A. Sarsah, 1E. Mensimah, 1E. Ampomah-Amoako,
1
R.B.M. Sogbadji and 1S.A. Birikorang
1
Ghana Atomic Energy Commission, National Nuclear Research Institute,
P.O. Box LG 80, Legon-Accra, Ghana
2
Ghana Atomic Energy Commission, Radiophamarcy and Nuclear Medicine Center,
P.O. Box LG 80, Legon-Accra, Ghana
Abstract: This study was conducted to investigate the occurrence and extent of potentially trace and major
elements in kaolin, widely used in Ghana, using the Instrumental Neutron Activation Analysis (INAA)
technique. Soil plays a vital role in human sustenance on earth. Different forms of soil have been used over the
years to solve pertinent requirements of man. Kaolin, commonly referred to as “hyire” in Ghana, has been used
by women during the delicate periods of their pregnancy and also by lactating mothers. This study has sought
to conduct an analysis of the toxic elements that may be ingested by these pregnant women when they eat”
hyire” using Instrumental Neutron Activation Analysis (INAA) at the Ghana Research Reactor-1 facility. The
study has shown that even though there are useful (major) elements present in the samples used, some toxic
elements were also found to be beyond the Recommended Dietary Allowance for those elements.
Recommendation has been made to request policy makers to regulate the production and use of “hyire” in order
that pregnant women and their foetus are not exposed to effects of the toxic components detected. Industries
have been encouraged to invest in this viable sector and to use modern technology to make the manufacturing
of “hyire” more refined.
Key words: Heavy metals, instrumental neutron activation analyses, trace elements
kaolin as fillers in paint, rubber, plastics and adhesives
and sealants and pharmaceuticals. Other important uses
include the manufacture of white cement and glass fibre
(Adamis and Williams, 2005).
People around the world eat clay, dirt or other pieces
of the lithosphere for a variety of reasons. Commonly, it
is a traditional cultural activity which takes place during
pregnancy, religious ceremonies, or as a remedy for
disease. Most people who eat dirt live in Central Africa
and the Southern United States. While it is a cultural
practice, it also fills a physiological need for nutrients.
In Ghana, kaolin which is locally known as ’’ hyire”,
is chalk-like in nature and it is very popular with pregnant
and lactating mothers as well as herbalists. The chalk can
be bought in ethnic shops and markets in the form of
blocks, pellets and powders (i.e., a variety of sizes and
with differing content of minerals). There are no
particular brands, batches or expiry dates. These “hyire”
samples are prepared by the native people depending on
what the sample will be used for. Some of them are burnt
in an oven whilst others are dried in the sun to have a
desired effect. It is traditionally consumed by the pregnant
women as remedy of morning sickness. Certain
INTRODUCTION
Kaolin which is also known as “China clay”, is a
natural claylike mineral (silicate of aluminum) and is
composed of silica, iron, magnesium, calcium, sodium
and other minerals.
Kaolin has also been used topically as an emollient
and drying agent. Specifically, it has been used to dry
oozing and weeping poison ivy, poison oak, and poison
sumac lesions. It has also been used as a protectant for the
temporary relief of anorectal itching and diaper rash.
Demand is most in the manufacture of paper where it
performs two separate functions- as a filler to improve
printing characteristics and as a coating pigment to
enhance the surface properties of the paper such as the
brightness, smoothness, gloss and ink receptivity etc.
(Taylor, 1998)
In the ceramics industry the main function of kaolin
is to impart whiteness. Its major uses are in vitreous china
sanitary ware, table ware, wall tiles and electrical
porcelain (Adamis and Williams, 2005).
Kaolin is used in refractories where it is valued for its
alumina content. Performance mineral applications use
Corresponding Author: R.G. Abrefah, Ghana Atomic Energy Commission, National Nuclear Research Institute, P.O. Box LG80,
Legon-Accra, Ghana. Tel.: +233-24-4653514
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Res. J. Appl. Sci. Eng. Technol., 3(8): 752-755, 2011
the reactor and allowed to decay for 1min (for short), 24
h (for medium) and 2 wks (for long) respectively. The
small irradiation vial containing the radioactive kaolin
sample was placed on the coaxial High Purity Germanium
(HPGe) semi-conductor (-ray detector (Canberra) and the
(-activity of the induced radioisotopes were measured.
Measurement time depended on the activities of the
induced radioisotopes. Similarly, measurement of the (activity of the induced radioisotopes produced in the
standard reference material was obtained on the same
coaxial HPGe ( -ray detector (and at the same sourcedetector distance). A plexiglass source support was
mounted on the detector during the measurement in order
to ensure easy and reproducible source positioning (DeCorte et al., 1987). The ORTEC MAESTRO-32 (spectroscopy software was used for ( -spectrum
acquisition.
additives are added to the base material to enhance their
potency. Pregnant and lactating women are able to satisfy
the very different nutritional needs of their bodies by
eating “hyire”. Traditionally, herbalists or native doctors
use “hyire” for the cure of diarrhea and other ailments. It
is necessary to investigate the composition of “hyire”
because it is ingested for both nutritional and medical
reason as any contamination might cause havoc.
The level of most of the constituents in various
“hyire” samples used by many Ghanaians is unknown.
Instrumental Neutron Activation Analysis (INAA) has
been used to analyze the elemental composition of six
different types of kaolin and their effects on the
individuals who ingest them.
MATERIALS AND METHODS
Instrumentation: Sample irradiations for neutron
activation analysis were carried out in the 30 kW
Miniature Neutron Source Reactor (MNSR) at a neutron
flux of 5 × 1011 neutrons/cm2s. The reactor is situated at
the Ghana Atomic Energy Commission, Kwabenya,
Accra, Ghana.
RESULTS AND DISCUSSION
The precision and accuracy of the analytical
technique (INAA) were assessed by simultaneous
activation of reference material IAEA soil-7 and NISTSRM 1646a Estuarine Sediment. Table 1 shows the
analytical results obtained for Al, As, Ca, Co, Fe, K, Mg,
Mn, Na, Sc, Ti and V at GHARR-1 laboratory for the
reference materials compared with the experimental
samples. The values obtained compared favourably well
with the recommended values. The experimental samples
were within ±5% of the recommended values. The
measurement precision specified by the relative standard
deviation was within ±4%. The error margins are standard
deviations.
The sample identifications were chosen based on the
specific use of the kaolin; the samples were labeled RT,
PB, PE, FT, EP and RG respectively. The samples RT, PB
and PE are all various varieties of kaolin that are eaten.
The samples FT and RT are basically used for medication
by native doctors and herbalists. However, the sample
label EP is eaten and used for medication as well. The
results obtained recorded essential elements (Na, Mg, V,
Al, Ca, K, Fe and Mn) and other toxic elements like As,
Ti, Co and Sc. Twenty-one inorganic elements made up
of 6 major minerals (Ca, Na, K, Mg, P and Cl) and 15
trace elements (As, Co, Cr, Cu, F, Fe, I, Mn, Mo, Ni, Se,
Si, Sn, V and Zn) are now considered as being essential to
human life. Each major mineral is required in several
hundred milligrams/day while the traces are required in
few milligrams daily (Linder, 1991). Table 2 describes the
mean values of elemental concentrations of the kaolin
samples with standard deviations
The levels of Mg in the kaolin sample were highest
for the samples that are used singularly for medication
and were lowest for the sample PB which is eaten.
Study design: “Hyire” samples were bought from the
local market place as well as ethnic shops in Accra and
Cape-coast for the study from June, 2010 to August,
2010. The samples were collected and placed in plastic
container which had previously been treated with 10%
nitric acid for 24 h and rinsed with de-ionised water. The
samples were kept over ice in an ice chest transported to
the laboratory and stored frozen at 4 degrees before use.
Sample preparation: The samples were ground to
powder and homogenized. It was stored frozen and later
freeze-dried to constant weight. 100 mg of each sample
was weighed and packaged. Similarly, 100 mg of standard
reference materials were weighed and packaged for
irradiation. The samples were placed in small irradiation
vials (diameter 1.6 cm and height 5.5 cm). The small
irradiation vials containing the samples and standards
were heat-sealed. Two standard reference materials with
certified values were used to validate the INAA method.
The reference materials were: IAEA-Soil-7 and NISTSRM 1646a Estuarine Sediment. The samples were then
sent for short, medium and long irradiations.
Sample irradiation and counting: Samples and
standards were transferred into the reactor via the
pneumatic transfer system at a pressure of 0.6 MPa. The
“hyire” samples were irradiated for 10s (for the short
lived radionuclides), 30 min (for the medium lived
radionuclides) and 1h (for the long lived radionuclides)
(IAEA-TECDOC-564, 1990). At the end of the
irradiation, the samples and standards were removed from
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Res. J. Appl. Sci. Eng. Technol., 3(8): 752-755, 2011
Table 1: Analytical results and recommended values of IAEA-SOIL 7, and NIST-SRM 1646a Estuarine Sediment certified reference materials (mg/kg)
IAEA-SOIL 7
NIST-SRM 1646a Estuarine Sediment
------------------------------------------------------------------------------------------------------------Element
reported
This study
reported
This study
46582
22970±180
22950±160
Al
47000#
As
13.4*
12.9
6.23±0.21
6.18±0.19
164020
5190±200
5168±195
Ca
163000#
Co
8.9*
8.6
5*
6
24991
20080±390
20078±395
Fe
25700#
#
11800
8640±160
8710±140
K
12100
11600
3880±90
3900±98
Mg
11300#
Mn
631*
646
234.5±2.8
242±3.2
2375
7410±170
7500±200
Naz
2400#
Sc
8.3*
7.9
5*
4
2980
4560±210
4615±197
Ti
3000#
V
66*
68
44.84±0.76
44.64±0.63
#
*: Non certified/recommended value, : Information value
Table 2: Mean values of elemental concentrations of the Kaolin samples with standard deviations (mg/kg, unless indicated otherwise)
SampleID
----------------------------------------------------------------------------------------------------------------------------------------------------------------------Elements RG
FT
RT
PB
EP
PE
Mg
13448±4825
7379±4646
2967±1348
955.80±143.37
1437±215.55
9430±364.8
V
60.16±9.57
0.89±0.1335
13.93±2.0895
127.71±10.41
52.23±9.86
141.55±11.45
Al
95547±508
82.75±36.13
2815±60.83
73879±429.42
48462±224.09
82268±354.63
Mn
ND
14.96±2.244
ND
ND
399.72±58.57
821±123.15
Ca
2958±443.7
1450±217.5
287.09±43.058
308±46.2
956.97±143.546
669.88±100.48
Na
11421±28.89
2169±12.36
376.1±7.11
600.88±8.21
3675±18.5
562.83±7.82
K
20401±530.14
21116±400.52
34328±488.78
35123±502.83
35575±642.52
31425±47.13
As
ND
7.48±2.6
617.44±2.53
18.53±2.71
1.78±0.267
ND
Ti
2088±704
ND
1826±414
3336±796
2178±844
6624±993.6
Sc
4.16±0.22
5.48±0.24
9.47±0.29
ND
8.30±0.29
9.38±0.32
Co
2.95±0.12
0.86±0.129
0.27±0.041
ND
28.67±2.83
0.71±0.107
Fe
0.87±0.19
1.88±0.28
0.97±0.20
ND
276575±3157
2.46±0.45
ND: Not-detected
The sample labeled RG has the highest level of Ca
(2958±443.7 mg/kg) and RT has the lowest level of Ca
(287.09±43.058 mg/kg). All the other samples had some
concentration of Ca which is essential for strong bones
and teeth. Some of the concentrations obtained are less
than the RDA of 1000 mg, however, continual intake of
these samples could increase the concentration of calcium
in the body.
Sodium levels also ranged from 376.1±7.11 to
11421±28.89 mg/kg. The Na levels in some of the
samples were below the RDA which is 1500 mg, but
higher in RG, FT and EP. Sodium is a systemic
electrolyte and is essential in co regulating ATP with
potassium (Nelson and Michael, 2000). Continual use will
lead to bioaccumulation thereby providing the RDA.
The kaolin samples have the very high levels of
potassium (20401±530.14 - 35575±642.52 mg/kg). The
RDA for potassium is 4700 mg which is way below the
values recorded in the sample. This is an indication that
the intake of any of the kaolin samples can assist in coregulating ATP with sodium.
Fe is also quite essential in the body. In the samples,
it has the highest concentration for the sample labeled EP
(eaten and medication) (276575±3157 mg/kg) and has the
lowest value (0.87±0.19 mg/kg) for RG (for medication).
The relatively high level of Fe obtained from the sample
However, the values obtained for all the samples were
higher than the Recommended Dietary Allowance (RDA)
of 420 mg (RDA, 1989). The high levels of Mg are
desirable as it is needed in the body for the secretion of
several enzymes.
Generally, the levels of V in the kaolin samples were
relatively low as compared to the other elements. The
level of V was highest in sample PE (which is eaten by
pregnant women) and lowest in sample FT (which is also
a variety that is used for medication). Vanadium has
established, albeit specialized, biochemical roles as
structural or functional cofactors in other organisms. This
element appears not to be utilized by humans (Lippard
and Berg, 1994)
Aluminium levels range from 95547±508 mg/kg in
RG to 82.75±36.13 mg/kg in FT. The levels are fairly
high in the samples
Manganese levels were not detected in some of the
samples. However, other samples recorded values of
14.96±2.244 mg/kg (being the least), 399.72±58.57 and
821±123.15 mg/kg. These values represent a variety of
sample that are eaten and also used for medication. The
RDA for Mn is 2.3 mg indicating that the Mn
concentrations obtained in these samples are way above
this value. Even though, Mn is a cofactor in enzyme
functions, an excess of it could cause manganism.
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Res. J. Appl. Sci. Eng. Technol., 3(8): 752-755, 2011
product is patronized by many Ghanaians, modern
industries could invest in the manufacture of this popular
product. These industries could make the manufacturing
process more refined with the use of modern methods
(this could help eliminate some of the contamination that
was obtained in the samples). The agencies responsible
for regulating food and drugs are alerted to take careful
look at the “hyire” on the Ghanaian market and provide
regulatory requirements for their producers to ensure safe
use of kaolin in Ghana.
EP in comparison with the Fe concentration in the other
kaolin samples could be attributed to the source of that
particular kaolin sample. It could be obtained from a
source that contains very high iron content. A particular
sample (PB, eaten by pregnant women) did not detect any
Fe concentration. Some of the samples recorded Fe
concentrations that were less than the RDA value for Fe
which is 8 mg. Insufficient Fe concentration in the body
will cause anemia whilst an excess of iron will cause iron
overload disorder.
Titanium concentrations with a range of 1826±414 to
6624±993.6 mg/kg were also detected in the kaolin
samples. Similarly, arsenic concentrations were detected
in some of the samples with values of 7.48±2.66,
17.44±2.53, 18.53±2.71 and 1.78±0.267 mg/kg being
recorded. Cobalt concentrations were also detected in
most of the kaolin samples. Their concentrations ranged
from 0.27±0.041to 28.67±2.83 mg/kg. Cobalt is required
in the synthesis of vitamin B12, but because bacteria are
required to synthesize the vitamin, it is usually considered
part of vitamin B12 deficiency rather than its own dietary
element deficiency. Excess cobalt in the human system
could also cause cobalt poisoning.
Finally, scandium concentrations were also recorded
in most of the samples. Values ranging from 0.87±0.19 to
9.47±0.29 mg/kg were recorded. This is an indication that
there is some contamination of the kaolin before it reaches
the final consumer either through preparation or storage.
ACKNOWLEDGMENT
We are grateful to Mr Opata at the Ghana Research
Reactor-1, Ghana Atomic Energy Commission for his
assistance during the irradiation and counting.
REFERENCES
Adamis, Z. and R.B. Williams, 2005. Bentonite, Kaolin
and Selected Clay Minerals, World Health
Organization, Geneva.
De-Corte, F., A. Simonits, A. De-Wispelaere and J.
Hoste, 1987. Accuracy and applicability of the k
standardization method, J. Radioanal. Chem., 113:
145-165.
Linder, M.C., 1991. Nutrition and Metabolism of the
Major Minerals, In: Linder, M.C. (Ed.), Nutrition
Biochemistry and Metabolism with Clinical
Applications, 2nd Edn., Elsevier, New York, USA,
pp: 151-198.
Lippard, S.J. and M.J. Berg, 1994. Principles of
Bioinorganic Chemistry. University Science Books,
Mill Valley, CA, pp: 411. ISBN: 0935702725.
Nelson, D.L. and M.C. Michael, 2000. Lehninger
Principles of Biochemistry. Freeman, W.H. (Ed.),
3rd Edn., pp: 1200, ISBN: 0444893075.
Practical Aspects of Operating Neutron Activation
Analyses Laboratory, 1990. IAEA-TECDOC-564,
Vienna, pp: 197.
Recommended Dietary Allowances (RDA), 1989. 10th
Edn., National Academy Press, Washington, D.C.,
pp: 1.
Taylor, P.W., 1998. Technical advances in kaolin
production for paper application, Tappi. J., 81(5):
79-82.
CONCLUSION
All the “hyire” samples chosen for this work contains
five major elements as well as other elements essential to
life. Some of these elements were detected in high
concentrations; hence the “hyire” samples are safe for
human consumption based on only the essential elements.
But As (in FT, RT and PB), Ti(in RG, RT, PB, EP and
PE), Co( in RG and EP), and Fe(EP) levels in the “hyire”
samples in the study area were a little higher considering
the fact that it is either eaten or used for medication.
These high levels could be attributed to contamination
introduced during the manufacturing process. Hence some
remediation interventions should be put in place in order
to reduce the levels of these elements in the finished
product It is also important for the sources of the additives
to be investigated to clarify its purity level. Since the
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